If you are considering using field-readable coded color markers on birds, consider the recommendations below. Please keep in mind that the BBL will get reports from the public who are very interested in where the bird came from and why it is marked. The BBL and BBO have an obligation to the public to respond to such reports. Following these recommendations will help tremendously.

Recommendations:
Use only unique code combinations per bird of a given species.
Do not use the same code for males and females of a species.
Do not use the same codes on opposite legs to differentiate between two birds, use unique code combinations for every bird.
Always use a consistent number of characters. For example, if you need two hundred unique combinations, use three digit codes for all combinations, 000-199, NOT 0-199.

We have a new code tracker system in the BBL permit database. It is helpful when you are choosing codes in sets of 100 to start with the number 0 and end with 9, for example use 00-99 for a hundred combinations, NOT 001-100. In general, when using solely alpha codes, change just the first letter in the combination to add more combinations and keep the codes in the 2nd ,3rd etc. position the same.

If possible, avoid using the following characters B,D,G,H,I,L,M,N,O,Q,S,U,V,W,X,Z. See these examples of look alikes*:

B=8
C=G=6
D=O=0=Q
H=H (is read the same upside down as upright; HX upside down is XH)
I=1=L
M=N
M=W
N=N (is read the same upside down as upright; NX upside down is XN)
S=5
U=V
X=X (is read the same upside down as upright; HX upside down is XH)
Z=2=7

*Also try to avoid “sound-alikes”. If you have a person looking through a scope and reading codes to a recorder, “M” and “N” and others can sound alike.